1. Field of the Invention
The present invention relates to an image sensing apparatus and a method for controlling the image sensing apparatus, and more particularly, relates to a technique for reducing a vertical linear noise in an image sensing apparatus and a method for controlling the image sensing apparatus.
2. Description of the Related Art
Conventionally, in CCD image sensors in which high speed sweep is carried out for sweeping unnecessary charge for each readout field, vertical linear noises which have a difference in level between the top and bottom of the screen may be caused as shown in FIG. 11A.
As an image sensing apparatus and a method for reducing vertical linear noises caused in these CCD image sensors, a technique is known which is described in Japanese Patent Application Laid-Open No. 2007-27864. Japanese Patent Application Laid-Open No. 2007-27864 discloses the storage of image data (FIG. 11B) into a memory, which is obtained by carrying out readout after the completion of exposure without transfer of charge from a light receiving element to a transfer unit, and then the reduction of vertical linear noises through the subtraction from image data obtained by transferring the charge from the light receiving element to the transfer unit and carrying out readout (FIG. 11C).
However, in accordance with the method disclosed in Japanese Patent Application Laid-Open No. 2007-27864, although vertical linear noises can be corrected the subtraction processing is carried out for all of the pixels. Thus, the subtraction processing is carried out even for pixels which require no subtraction processing, thereby degrading the S/N ratio.